Field of the Invention
The present invention relates to an electric discharge machine with a rotary table.
Description of the Related Art
A rotary table used in an electric discharge machine is disposed on a workpiece table in a machining tank that is filled with a machining fluid, and a workpiece as an object of electric discharge machining is fixed on a face plate of the rotary table. Since the machining tank in which the rotary table is placed is limited in size, the rotary table should be as compact as possible. Since the workpiece is sometimes secured directly to the workpiece table in the machining tank, moreover, the rotary table should also be lightweight so that an operator can easily attach and remove it.
An example of the rotary table of an electric discharge machine (see Japanese Patent Application Laid-Open No. 2003-25154) will now be described with reference to FIG. 4.
A power unit 2, first pulley 3, and second pulley 4 are set in a rotary table 1. The power unit 2 and the first pulley 3 are disposed on the same axis (C-axis 7) and can rotate synchronously. A belt 5 is stretched between the first and second pulleys 3 and 4 such that the rotation of the power unit 2 can be transmitted to the second pulley 4 through the first pulley 3.
On the other hand, a face plate 6 for securing a workpiece (not shown) is mounted outside the rotary table 1. The face plate 6 and the second pulley 4 are disposed on the same axis (D-axis 8) and can rotate synchronously. Thus, the power unit 2 and the face plate 6 can rotate synchronously.
Further, Japanese Patent No. 3862956 (corresponding to WO2000/024541) discloses a technique on a spindle device of a die-sinking electric discharge machine, capable of minimizing the parts count by disposing units ranging from a power unit to a mounting unit (equivalent to a face plate) on the same straight line.
However, the rotary table disclosed in Japanese Patent Application Laid-Open No. 2003-25154 shown in FIG. 4 has the two axes, the C- and D-axes 7 and 8, which require the use of two bearings (not shown) and a space for securing the bearings. Thus, it is difficult to construct a compact, lightweight rotary table.
According to the technique disclosed in Japanese Patent No. 3862956, moreover, the power unit and the mounting unit are simply arranged in series, so that the axial dimension of the device is inevitably large.